conduit practices in class 1, div 2 areas 1

[mike4168]

I am installing equipment in a hazardous (C1, D2) location. All the instrumentation is XP rated for this area. The enclosure is also located in this classified area. The enclosure is a NEMA 12 type with an argon purge. As I interpret my NEC manual, that should be suitable. I have used seals and meyers hubs to enter this enclosure. I have two "junction boxes" (NEMA 12, no purge)mounted closer to the action that are used simply as a manifold for routing cables to the individual instruments from a couple of conduits. Keep in mind that no terminations are made in these "junction boxes". If the terminal chambers on the instruments are XP rated (I believe that means they are rated to contain an explosion), do I need to use seals at the entrance to these terminal chambers? If so, then I have an alternate question. I have read a reply to someone's question concerning seal-tite and EMT conduit stating that EMT could not be used, and that seal-tite was limited to 6 feet for grounding purposes. If I use seals and supply a sufficient ground wire, then what is in between shouldn't matter, except for physical protection. Sorry I'm so long, but I do appreciate any advice.

 

[dpc]

Mike,

I don't think you can ever use EMT in classified area for any purpose, regardless of seals, etc. Conduit fittings and couplings must be threaded, and EMT can not be threaded. Refer to NEC Article 501.

Also, your liquid-tight flexible metal conduit must use listed fittings in Class I, Div II locations.

I'm not clear on the type of instrumentation or what is in the enclosure. If there are no arc-producing contacts on the instruments, then I don't believe they need to be explosion-proof. If there are no contacts mounted in the enclosure, a general-purpose enclosure can be used.

 

[geo57]

Mike,

I've seen instrument connections with and without seals. You are not required to install the seals on analog devices, although several companies private standards require them. The sealtite is limited to the six feet, and I use connectors with the external bonding jumpers, they make a sealtite that is internally bonded, although I perfer the external bonding jumper as it is easy to see on inspection.
Do not use EMT for hazardous area's. One other point is that many of the discrete devices such as presure switches are available as factory sealed, you may want check into the devices you have before you install seals.
Code also requires when using a Z purge, which is what you have done, you need to installl a loss of purge alarm. Most purge kits (Bebco, Expo, Etc. ) come with the pressure switches mounted on them.

Hope this helps

 

[tomd87vr]

Happened to find this discussion refering to class1-div2 specs. I work for an OEM of custom mfg machinery. We are not familiar with the class1-div2 spec which a customer has requested in a recent RFQ. Where/how can I obtain this info?
Thanks for any reponses